The number of users enjoying online games such as a massive multiplayer online role playing game (MMORPG) is increasing. For example, the number of users of World of Warcraft, managed by Blizzard® Entertainment in the U.S., exceeds 12 million around the world. As the numbers of users enjoying the online games increases as stated above, scale-out using cloud computing systems becomes important.
However, the existing infrastructures for implementing a cloud computing environment are typically adapted to business applications, such as an e-mail application and a word processor, that run on personal computers, so that it is difficult to efficiently implement an online game. Specifically, since an online game such as an MMORPG requires real-time transfer of information to clients in a virtual world, communication between the database server and a game server tends to become a bottleneck.